This document will help you configure,
make,
test and install Perl on Cygwin.
This document also describes features of Cygwin that will affect how Perl behaves at runtime.

NOTE: There are pre-built Perl packages available for Cygwin and a version of Perl is provided in the normal Cygwin install.
If you do not need to customize the configuration,
consider using one of those packages.

The Cygwin tools are ports of the popular GNU development tools for Win32 platforms.
They run thanks to the Cygwin library which provides the UNIX system calls and environment these programs expect.
More information about this project can be found at:

While building Perl some changes may be necessary to your Cygwin setup so that Perl builds cleanly.
These changes are not required for normal Perl usage.

NOTE: The binaries that are built will run on all Win32 versions.
They do not depend on your host system (Win9x/WinME,
WinNT/Win2K) or your Cygwin configuration (ntea,
ntsec,
binary/text mounts).
The only dependencies come from hard-coded pathnames like /usr/local.
However,
your host system and Cygwin configuration will affect Perl's runtime behavior (see "TEST").

PATH

Set the PATH environment variable so that Configure finds the Cygwin versions of programs.
Any Windows directories should be removed or moved to the end of your PATH.

nroff

If you do not have nroff (which is part of the groff package),
Configure will not prompt you to install man pages.

Permissions

On WinNT with either the ntea or ntsecCYGWIN settings,
directory and file permissions may not be set correctly.
Since the build process creates directories and files,
to be safe you may want to run a chmod -R +w * on the entire Perl source tree.

Also,
it is a well known WinNT "feature" that files created by a login that is a member of the Administrators group will be owned by the Administrators group.
Depending on your umask,
you may find that you can not write to files that you just created (because you are no longer the owner).
When using the ntsecCYGWIN setting,
this is not an issue because it "corrects" the ownership to what you would expect on a UNIX system.

It is possible to strip the EXEs and DLLs created by the build process. The resulting binaries will be significantly smaller. If you want the binaries to be stripped, you can either add a -s option when Configure prompts you,

Any additional ld flags (NOT including libraries)? [none] -s
Any special flags to pass to g++ to create a dynamically loaded library?
[none] -s
Any special flags to pass to gcc to use dynamic linking? [none] -s

or you can edit hints/cygwin.sh and uncomment the relevant variables near the end of the file.

Several Perl functions and modules depend on the existence of some optional libraries. Configure will find them if they are installed in one of the directories listed as being used for library searches. Pre-built packages for most of these are available from the Cygwin installer.

NOTE: The BerkeleyDB library only completely works on NTFS partitions and db-4.3 is flawed.

cygserver (use IPC::SysV)

A port of SysV IPC is available for Cygwin.

NOTE: This has not been extensively tested. In particular, d_semctl_semun is undefined because it fails a Configure test and on Win9x the shm*() functions seem to hang. It also creates a compile time dependency because perl.h includes <sys/ipc.h> and <sys/sem.h> (which will be required in the future when compiling CPAN modules). CURRENTLY NOT SUPPORTED!

-lutil

Included with the standard Cygwin netrelease is the inetutils package which includes libutil.a.

The INSTALL document describes several Configure-time options. Some of these will work with Cygwin, others are not yet possible. Also, some of these are experimental. You can either select an option when Configure prompts you or you can define (undefine) symbols on the command line.

-Uusedl

Undefining this symbol forces Perl to be compiled statically.

-Uusemymalloc

By default Perl uses the malloc() included with the Perl source. If you want to force Perl to build with the system malloc() undefine this symbol.

-Uuseperlio

Undefining this symbol disables the PerlIO abstraction. PerlIO is now the default; it is not recommended to disable PerlIO.

-Dusemultiplicity

Multiplicity is required when embedding Perl in a C program and using more than one interpreter instance. This works with the Cygwin port.

-Duse64bitint

By default Perl uses 32 bit integers. If you want to use larger 64 bit integers, define this symbol.

-Duselongdouble

gcc supports long doubles (12 bytes). However, several additional long double math functions are necessary to use them within Perl ({atan2, cos, exp, floor, fmod, frexp, isnan, log, modf, pow, sin, sqrt}l, strtold). These are not yet available with Cygwin.

-Dusethreads

POSIX threads are implemented in Cygwin, define this symbol if you want a threaded perl.

-Duselargefiles

Cygwin uses 64-bit integers for internal size and position calculations, this will be correctly detected and defined by Configure.

-Dmksymlinks

Use this to build perl outside of the source tree. This works with Cygwin. Details can be found in the INSTALL document. This is the recommended way to build perl from sources.

Win9x does not correctly report EOF with a non-blocking read on a closed pipe. You will see the following messages:

But it also returns -1 to signal EOF, so be careful!
WARNING: you can't distinguish between EOF and no data!
*** WHOA THERE!!! ***
The recommended value for $d_eofnblk on this machine was "define"!
Keep the recommended value? [y]

At least for consistency with WinNT, you should keep the recommended value.

Compiler/Preprocessor defines

The following error occurs because of the Cygwin #define of _LONG_DOUBLE:

The same tests are run both times, but more information is provided when running as ./perl harness.

Test results vary depending on your host system and your Cygwin configuration. If a test can pass in some Cygwin setup, it is always attempted and explainable test failures are documented. It is possible for Perl to pass all the tests, but it is more likely that some tests will fail for one of the reasons listed below.

UNIX file permissions are based on sets of mode bits for {read,write,execute} for each {user,group,other}. By default Cygwin only tracks the Win32 read-only attribute represented as the UNIX file user write bit (files are always readable, files are executable if they have a .{com,bat,exe} extension or begin with #!, directories are always readable and executable). On WinNT with the nteaCYGWIN setting, the additional mode bits are stored as extended file attributes. On WinNT with the default ntsecCYGWIN setting, permissions use the standard WinNT security descriptors and access control lists. Without one of these options, these tests will fail (listing not updated yet):

Cygwin does an outstanding job of providing UNIX-like semantics on top of Win32 systems. However, in addition to the items noted above, there are some differences that you should know about. This is a very brief guide to portability, more information can be found in the Cygwin documentation.

Pathnames

Cygwin pathnames can be separated by forward (/) or backward (\\) slashes. They may also begin with drive letters (C:) or Universal Naming Codes (//UNC). DOS device names (aux, con, prn, com*, lpt?, nul) are invalid as base filenames. However, they can be used in extensions (e.g., hello.aux). Names may contain all printable characters except these:

: * ? " < > |

File names are case insensitive, but case preserving. A pathname that contains a backslash or drive letter is a Win32 pathname (and not subject to the translations applied to POSIX style pathnames).

For conversion we have Cygwin::win_to_posix_path() and Cygwin::posix_to_win_path().

Pathnames may not contain Unicode characters. Cygwin still uses the ANSI API calls and no Unicode calls because of newlib deficiencies. There's an unofficial unicode patch for cygwin at http://www.okisoft.co.jp/esc/utf8-cygwin/

Text/Binary

When a file is opened it is in either text or binary mode. In text mode a file is subject to CR/LF/Ctrl-Z translations. With Cygwin, the default mode for an open() is determined by the mode of the mount that underlies the file. See Cygwin::is_binmount(). Perl provides a binmode() function to set binary mode on files that otherwise would be treated as text. sysopen() with the O_TEXT flag sets text mode on files that otherwise would be treated as binary:

sysopen(FOO, "bar", O_WRONLY|O_CREAT|O_TEXT)

lseek(), tell() and sysseek() only work with files opened in binary mode.

The text/binary issue is covered at length in the Cygwin documentation.

PerlIO

PerlIO overrides the default Cygwin Text/Binary behaviour. A file will always be treated as binary, regardless of the mode of the mount it lives on, just like it is in UNIX. So CR/LF translation needs to be requested in either the open() call like this:

open(FH, ">:crlf", "out.txt");

which will do conversion from LF to CR/LF on the output, or in the environment settings (add this to your .bashrc):

export PERLIO=crlf

which will pull in the crlf PerlIO layer which does LF -> CRLF conversion on every output generated by perl.

.exe

The Cygwin stat(), lstat() and readlink() functions make the .exe extension transparent by looking for foo.exe when you ask for foo (unless a foo also exists). Cygwin does not require a .exe extension, but gcc adds it automatically when building a program. However, when accessing an executable as a normal file (e.g., cp in a makefile) the .exe is not transparent. The install included with Cygwin automatically appends a .exe when necessary.

Cygwin vs. Windows process ids

Cygwin processes have their own pid, which is different from the underlying windows pid. Most posix compliant Proc functions expect the cygwin pid, but several Win32::Process functions expect the winpid. E.g. $$ is the cygwin pid of /usr/bin/perl, which is not the winpid. Use Cygwin::winpid_to_pid() and Cygwin::winpid_to_pid() to translate between them.

Cygwin vs. Windows errors

Under Cygwin, $^E is the same as $!. When using Win32 API Functions, use Win32::GetLastError() to get the last Windows error.

chown()

On WinNT chown() can change a file's user and group IDs. On Win9x chown() is a no-op, although this is appropriate since there is no security model.

Miscellaneous

File locking using the F_GETLK command to fcntl() is a stub that returns ENOSYS.

Win9x can not rename() an open file (although WinNT can).

The Cygwin chroot() implementation has holes (it can not restrict file access by native Win32 programs).

Inplace editing perl -i of files doesn't work without doing a backup of the file being edited perl -i.bak because of windowish restrictions, therefore Perl adds the suffix .bak automatically if you use perl -i without specifying a backup extension.

Using fork() after loading multiple dlls may fail with an internal cygwin error like the following:

Use the rebase utility to resolve the conflicting dll addresses. The rebase package is included in the Cygwin netrelease. Use setup.exe from http://www.cygwin.com/setup.exe to install it and run rebaseall.

Returns the mount type and flags for a specified mount point. A comma-separated string of mntent->mnt_type (always "system" or "user"), then the mntent->mnt_opts, where the first is always "binmode" or "textmode".

These are the files in the Perl release that contain references to Cygwin. These very brief notes attempt to explain the reason for all conditional code. Hopefully, keeping this up to date will allow the Cygwin port to be kept as clean as possible.

Support for swapping real and effective user and group IDs is incomplete. On WinNT Cygwin provides setuid(), seteuid(), setgid() and setegid(). However, additional Cygwin calls for manipulating WinNT access tokens and security contexts are required.